Artículo
11/17/2011

DynamicMethod.CreateDelegate Method (Type)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Completes the dynamic method and creates a delegate of the specified type, which can be used to execute the dynamic method.

Namespace: System.Reflection.Emit
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
<ComVisibleAttribute(True)> _
<SecuritySafeCriticalAttribute> _
Public Overrides NotOverridable Function CreateDelegate ( _
    delegateType As Type _
) As Delegate

[ComVisibleAttribute(true)]
[SecuritySafeCriticalAttribute]
public override sealed Delegate CreateDelegate(
    Type delegateType
)

Parameters

delegateType
Type: System.Type
A delegate type whose signature matches that of the dynamic method.

Return Value

Type: System.Delegate
A delegate of the specified type, which can be used to execute the dynamic method.

Exceptions

Exception	Condition
InvalidOperationException	The dynamic method has no method body.
ArgumentException	delegateType has the wrong number of parameters or the wrong parameter types.

Remarks

Calling the CreateDelegate method or the Invoke method completes the dynamic method. Any further attempt to alter the dynamic method, such as modifying parameter definitions or emitting more Microsoft intermediate language (MSIL), is ignored; no exception is thrown.

Examples

The following example demonstrates the use of the CreateDelegate(Type) method overload to create a delegate to execute a simple dynamic method. The method has two parameters, a format string and an integer. The method calls the String.Format(String, Object) method overload with these two arguments, and returns the result.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Reflection.Emit
Imports System.Reflection

Public Class Example

   ' Declare a delegate that can be used to execute the dynamic method.
   Private Delegate Function Caller(ByVal msg As String, _
        ByVal number As Integer) As String

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Create an array that specifies the types of the parameters
      ' of the dynamic method. This method has a String parameter
      ' and an Integer parameter.
      Dim paramTypes() As Type = { GetType(String), GetType(Integer) }

      ' Create an unnamed dynamic method with a return type of
      ' Integer and with two parameters whose types are specified by
      ' the array paramTypes. The dynamic method is anonymously
      ' hosted. 
      Dim method As New DynamicMethod("", GetType(String), paramTypes)

      ' Get a MethodInfo for the overload of String.Format that
      ' takes a format string and an object for insertion in the format 
      ' string. The dynamic method uses this overload to format the 
      ' return string.
      Dim stringFormat As MethodInfo = GetType(String). _
          GetMethod("Format", New Type() { GetType(String), GetType(Object) })

      ' Get an ILGenerator and emit a body for the dynamic method.
      Dim il As ILGenerator = method.GetILGenerator()

      ' Load the arguments onto the execution stack. The second 
      ' argument is an Integer, so it must be boxed before it can be 
      ' passed to a parameter of type Object. 
      il.Emit(OpCodes.Ldarg_0)
      il.Emit(OpCodes.Ldarg_1)
      il.Emit(OpCodes.Box, GetType(Integer))

      ' Call the String.Format method. The return value from that call 
      ' is placed on the execution stack, so the dynamic method simply 
      ' returns.         
      il.Emit(OpCodes.Call, stringFormat)
      il.Emit(OpCodes.Ret)

      ' Create a delegate that represents the dynamic method. This
      ' action completes the dynamic method, and any further attempts
      ' to change the method have no effect.
      Dim callMethod As Caller = method.CreateDelegate(GetType(Caller))

      ' Invoke the delegate and display the result.
      Dim ret As String = callMethod("The second argument is: {0}.", 1969)

      outputBlock.Text &= _
         String.Format("Invoking the delegate returned the string '{0}'.", ret)

   End Sub

End Class

' This code example produces the following output:
'
'Invoking the delegate returned the string 'The second argument is: 1969.'.

using System.Reflection.Emit;
using System.Reflection;
using System;

public class Example
{
   // Declare a delegate that can be used to execute the dynamic method.
   private delegate string Caller(string msg, int number);

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create an array that specifies the types of the parameters
      // of the dynamic method. This method has a String parameter
      // and an Integer parameter.
      Type[] paramTypes = { typeof(string), typeof(int) };

      // Create an unnamed dynamic method with a return type of
      // Integer and with two parameters whose types are specified by
      // the array paramTypes. The dynamic method is anonymously
      // hosted. 
      DynamicMethod method = new DynamicMethod("", typeof(string), paramTypes);

      // Get a MethodInfo for the overload of String.Format that
      // takes a format string and an object for insertion in the format 
      // string. The dynamic method uses this overload to format the 
      // return string.
      MethodInfo stringFormat = typeof(string).GetMethod("Format", 
         new Type[] { typeof(string), typeof(object) });

      // Get an ILGenerator and emit a body for the dynamic method.
      ILGenerator il = method.GetILGenerator();

      // Load the arguments onto the execution stack. The second 
      // argument is an Integer, so it must be boxed before it can be 
      // passed to a parameter of type Object. 
      il.Emit(OpCodes.Ldarg_0);
      il.Emit(OpCodes.Ldarg_1);
      il.Emit(OpCodes.Box, typeof(int));

      // Call the String.Format method. The return value from that call 
      // is placed on the execution stack, so the dynamic method simply 
      // returns.         
      il.Emit(OpCodes.Call, stringFormat);
      il.Emit(OpCodes.Ret);

      // Create a delegate that represents the dynamic method. This
      // action completes the dynamic method, and any further attempts
      // to change the method have no effect.
      Caller callMethod = (Caller) method.CreateDelegate(typeof(Caller));

      // Invoke the delegate and display the result.
      string ret = callMethod("The second argument is: {0}.", 1969);

      outputBlock.Text += 
         String.Format("Invoking the delegate returned the string '{0}'.", ret);
   }
}

/* This code example produces the following output:

Invoking the delegate returned the string 'The second argument is: 1969.'.
 */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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